083
FXUS10 KWNH 200426
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1225 AM EDT WED MAY 20 2020
VALID MAY 20/0000 UTC THRU MAY 23/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CUT-OFF LOW OVER LOWER OH AND TN RIVER VALLEYS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z GFS BLEND BEYOND 22.00Z
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
MODELS HAVE CONVERGED ON A SIMILAR SOLUTION FOR THE EVOLUTION OF
THE LARGE CUT-OFF LOW OVER THE LOWER OH AND TN RIVER VALLEYS
THROUGH FRIDAY MORNING. GRADUALLY THE LOW BEGINS TO FILL AND WITH
THE APPROACHING UPPER TROUGH ACROSS THE CENTRAL PLAINS, ITS ENERGY
BECOMES ABSORBED. HOWEVER, THIS IS WHERE THE MODELS DIFFER, WHERE
THE GFS ALLOWS THIS TO HAPPEN MUCH FASTER THAN THE OTHER GUIDANCE,
DUE TO THE FASTER PROGRESSION OF THE TROUGH AXIS OVER THE INTERIOR
WEST AND ROCKIES. THE OTHER GUIDANCE (ECMWF/UKMET) SHOW A SLOWER
PROGRESSION WITH THE LOW REMAINING CUT-OFF THROUGH MUCH OF THE
PERIOD. THE 12Z CMC WAS UNAVAILABLE FOR ANALYSIS AND NOT INCLUDED
IN THIS DISCUSSION.
GIVEN THE OUTLIER SOLUTION IN THE 00Z GFS, THE WPC BLEND
PREFERENCE WILL REMAIN FOR A NON-GFS SOLUTION BEYOND 22.00Z,
PRIMARILY COMPOSED OF THE ECMWF/UKMET DETERMINISTIC SOLUTIONS.
..DEEP UPPER TROUGH/CLOSED LOW OVER THE WESTERN U.S. WEDNESDAY
..SECONDARY UPPER TROUGH OVER THE PACIFIC NORTHWEST BY THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NAM/ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE
THE LATEST GUIDANCE SHOWS AVERAGE TO SLIGHTLY ABOVE AVERAGE
AGREEMENT FOR THE LONGWAVE TROUGH OVER THE WEST THAT WILL LIFT
TOWARD THE NORTHERN ROCKIES OVER THE NEXT 1-2 DAYS. TOWARD DAY
2/3, ANOTHER SHORTWAVE DROPPING SOUTHEAST OVER THE PAC NW ABSORBS
THE INITIAL WAVE AND FORMS A LARGE CLOSED LOW WITH SEVERAL LOBES
OF VORTICITY PIVOTING AROUND THE CENTER. IN THE LARGE SCALE SENSE,
THE MODELS ALL HAVE THIS SCENARIO, HOW EACH INDIVIDUAL VORT MAX
PLAYS OUT DIFFERS IN STRENGTH AND PLACEMENT. OVERALL, THE GFS WAS
THE LEAST FAVORED AS ITS 1) FASTER THAN THE REST OF THE GUIDANCE
AND 2) AMPLIFIES THE TWO SHORTWAVES TOGETHER EARLIER. THE NAM
APPEARS USEFUL THROUGH ABOUT 60 HOURS AND THEN SHOWS SOME LAGGING
COMPARED TO THE ECMWF/UKMET AND ENSEMBLE MEANS. THE CMC WAS NOT
CONSIDERED IN THIS ANALYSIS DUE TO DATA FLOW PROBLEMS. OVERALL,
THE WPC BLEND PREFERENCE IS FOR A NEAR EQUAL WEIGHTING OF THE
NAM/ECMWF/UKMET.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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